Sunday, October 26, 2014

Eclipse - Highlight of a Long Thursday!

As the last post mentioned, we had a nice solar eclipse Thursday.  Only a partial with just over 40% of the Sun and Moon's disks overlapped in Tucson, but a good excuse to go out and observe the sun.  My friend Bob, visiting from Ohio, had scheduled an "Astronomer Night" at the University of Arizona's Mount Lemmon SkyCenter with their 32" Schulman telescope.  The program was for up to two attendees, and he invited me to join him for a night of CCD imaging - I didn't need to be asked twice!  Unfortunately, the day started early with Melinda's 4th cycle of her current round of chemo at 7:30, so with pulling an all-nighter, it would be a memorable day!

Image courtesy Travis Deyoe/Mt Lemmon SkyCenter/University of Arizona
After Melinda's treatments, Bob and I headed up the mountain a little before 1pm, stopping for snacks and gas before leaving town.  We arrived about 3, the solar eclipse already well under way.  By the time I set up my little tripod-mounted vintage Celestron 5", it was nearing mid-eclipse.  The focal length of over 1200mm is perfect for the Sun and Moon, yet is easy to carry, setup and move.  Even with the solar filter in front, exposures were short enough (300th second), that tracking wasn't needed, though the telescope had to be moved frequently to keep the Sun centered.  Setup is shown at left, and in the background, the staff at the SkyCenter was using a pair of telescopes.  One was for visual observing, the other for streaming images to the Internet. 

Shown at right is an image from their sequence about the time we arrived.  This is the view from a Hydrogen-Alpha telescope - an image from a single red wavelength that shows solar activity due to hydrogen reactions.  The magnetic fields associated with sunspots can throw up loops of plasma, seen as "flames", called prominences at the edge of the Sun's disk. When these same prominences are seen silhouetted against the disk, they appear as darker filaments.  The image was converted to black and white and contrast-adjusted to better show both the edge and disk details.

Compare that image to the "white light" view of the eclipse through my C5 with solar filter taken at about the same time at left.  Note that the "flames" at the edge (prominences) are not visible in white light images, and though the sunspot views are different, the fine details in each image are complementary, each showing spectacular details!  Arriving near mid-eclipse as we did, it was impossible to catch earlier phases, but at right is a trio of images taken at 20 minute intervals showing the motion of the moon past the sun.  In all these images, north is approximately up and the local time is indicated.

Note also by clicking the image to load the full-size image, that the Moon's edge is not smooth.  Some of that is due to seeing effects of atmospheric turbulence, but some of it is also due to mountains and valleys along the edge of the Moon's profile.  One of the fun things for me to observe at almost any Moon phase are the bumps and wiggles of its edge profile.

As I mentioned in my previous post, with about 40% of the disks overlapping, much more of the sun's area was exposed, and I didn't really see any outward signs of an eclipse occurring.  It would have had to be much more coverage to detect darkening of the sky.  Shadows cast by the trees formed pinhole-like images of the crescent on the ground and against the telescope domes.  I grabbed the binoculars and demonstrated another safe way of observing the eclipse if the special solar eclipse-viewing glasses were not available - project an image on a screen, or in this case, my card table.  Note in the close-up ahown at right, even the large sunspot is easily seen.  Note also that the arrow points to an "accidental" pinhole projection caused by the strap also casts a crescent shadow!

As I mentioned, this was just the appetizer of a very long day's observing - stay tuned for a couple more posts!

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